Nowadays, computer systems become essential parts in our daily lives. With rapid development of the computer systems, the computer peripheral devices which are closely related to the computer systems are gradually developed. For example, a scanning apparatus is one of the widely-used computer peripheral devices. Generally, the scanning apparatus is used for scanning images of paper documents. Consequently, the contents of the paper documents can be converted into electronic files. The electronic files may be further spread, managed or stored by the user. With the maturity of scanning technologies, the scanning apparatuses have experienced great growth and are now rapidly gaining in popularity.
In the early stage, the scanning apparatus can only scan the image of a single document. For scanning a stack of documents, after the image of the document is scanned, the document is removed and then a next document is placed on the scanning apparatus in order to scan the image of the next document. Since the process of manually replacing the documents is very troublesome, the conventional scanning apparatus is not feasible to scan a stack of documents. For solving these drawbacks, an automatic document feeder is introduced into the market. The automatic document feeder and the scanning apparatus are collaboratively defined as a sheet-feeding type scanning apparatus. By the sheet-feeding type scanning apparatus, it is not necessary to manually replace the documents while the scanning operations are performed. In other words, by the sheet-feeding type scanning apparatus, the stack of documents can be effectively scanned or even the duplex scanning operations on the documents may be performed.
Generally, a calibration plate is included in a flatbed scanning portion of the scanning apparatus. Before a scanning operation is performed, a calibrating operation may be performed by scanning the calibration plate in order to correct the errors from the optical and electronic system of the scanning apparatus. The optical and electronic system includes for example a light source, a lens and an optical sensing element. Generally, the calibrating operation includes for example a color calibrating operation, a brightness calibrating operation or a contrast calibrating operation.
Hereinafter, a process of calibrating the flatbed scanning portion of a conventional apparatus will be illustrated with reference to FIG. 1. FIG. 1 schematically illustrates the structure of a flatbed scanning portion of a conventional apparatus. As shown in FIG. 1, the conventional flatbed scanning portion 1 comprises a casing 10, a glass platform 11, a scanning module 12, a transmission mechanism 13, and a connecting element 14. Moreover, the scanning module 12 comprises a calibration plate 120, a light source 121, a reflective mirror 122, a lens 123, and an optical sensing element 124. Take the color calibrating operation for example. The calibration plate 120 may have a white color or a black color. That is, the calibration plate 120 may be used as a standard white reference plate or a standard black reference plate. As shown in FIG. 1, the calibration plate 120 has a white color and is served as a standard white reference plate.
Before a document (not shown) is scanned by the flatbed scanning portion 1 of the conventional scanning apparatus, the document is placed on the glass platform 11. The scanning module 12 is connected with the transmission mechanism 13 through the connecting element 14. The transmission mechanism 13 is driven to move the scanning module 12 along the glass platform 11. That is, the scanning module 12 is moved in a moving direction D to the location under the calibration plate 120. Meanwhile, a light beam B emitted from the light source 121 is projected on the calibration plate 120. The light beam B is reflected by the calibration plate 120, and subsequently reflected by the reflective mirror 122. The light beam B is then transmitted through and focused by the lens 123. The focused light beam B is received by the optical sensing element 124, and then the optical signal is converted into an electronic signal by the optical sensing element 124. Moreover, in the conventional flatbed scanning portion 1 of FIG. 1, the light source 121 is a light emitting diode (LED), and the optical sensing element 124 is a charge coupled device (CCD) or a contact image sensor (CIS).
In such way, a standard white value corresponding to the calibration plate 120 is acquired by the flatbed scanning portion 1. The standard white value is used as a white color basis. After the color calibrating operation is completed, the document (not shown) placed on the glass platform 11 is scanned by the flatbed scanning portion 1. Since the standard white value provided by the calibration plate 120 is severed as a basis of scanning the white region, the scanned image may be subject to calibrating compensation.
The process of calibrating the conventional flatbed scanning portion has been mentioned above. The process of calibrating the sheet-feeding type scanning apparatus, which is a combination of the conventional flatbed scanning portion and an automatic document feeder, is similar to the process of calibrating the conventional flatbed scanning portion. Generally, most of the current sheet-feeding type scanning apparatuses have a duplex scanning function. The sheet-feeding type scanning apparatuses with the duplex scanning function are also referred as duplex scanning apparatuses. Moreover, the duplex scanning apparatuses may be classified into two types. The first type duplex scanning apparatus is a duplex scanning apparatus with a single scanning module. The second type duplex scanning apparatus is a duplex scanning apparatus with two scanning modules.
FIG. 2 is a schematic side view illustrating the structure of a conventional first type duplex scanning apparatus. As shown in FIG. 2 the conventional first type duplex scanning apparatus 2 comprises a flatbed scanning portion 20 and an automatic document feeder 21. The flatbed scanning portion 20 comprises a scanning module 201 and a glass platform 202. The structure of the flatbed scanning portion 20 is similar to that of the conventional flatbed scanning portion 1 of FIG. 1, and is not redundantly described herein. Moreover, the automatic document feeder 21 comprises a sheet input tray 211, a sheet output tray 212, a sheet pick-up module 213, a sheet transfer channel 214, plural transfer rollers 215, a switching element 216, an inverting region 217, an inverting channel 218, and a sheet ejecting roller assembly 219.
The process of performing a duplex scanning operation by the conventional first type duplex scanning apparatus 2 will be illustrated as follows. Firstly, plural documents 22 to be scanned are placed on the sheet input tray 211, wherein the first sides 221 of the documents 22 face upwardly. Then, the uppermost document 22 is fed into the sheet transfer channel 214 by the sheet pick-up module 213 of the automatic document feeder 21. Then, the document 22 is transferred through the scanning module 201 by the plural transfer rollers 215, wherein the first side 221 of the document 22 faces the scanning module 201. The image of the first side 221 of the document 22 is read by the scanning module 201, so that a first side image is acquired. By the way, while the duplex scanning operation is performed by the conventional first type duplex scanning apparatus 2, the scanning module 201 is not movable along the glass platform 202.
After the first side 221 of the document 22 has been scanned, the document 22 is transported into the inverting region 217 by the plural transfer rollers 215 and the sheet ejecting roller assembly 219. By swinging the switching element 216 to open the channel, the document 22 is introduced into the inverting region 217 or ejected to the sheet output tray 212. In a case that the document 22 is introduced into the inverting region 217, the switching element 216 is swung and the document 22 is transported into the inverting channel 218 by the sheet ejecting roller assembly 219. After the document 22 is transferred through the inverting channel 218, the document 22 is transferred through the scanning module 201, wherein a second side 222 of the document 22 faces the scanning module 201. When the document 22 is transferred through the scanning module 201, the image of the second side 222 of the document 22 is read by the scanning module 201, so that a second side image is acquired.
After the second side 222 of the document 22 has been scanned, the document 22 is transported into the inverting region 217 again and then transported into the inverting channel 218 again. Consequently, the document 22 is transferred through the scanning module 201 again, wherein the first side 221 of the document 22 faces the scanning module 201. Under this circumstance, the image of the first side 221 of the document 22 is not scanned by the scanning module 201. Then, the document 22 is ejected to the sheet output tray 212 through the switching element 216. Meanwhile, the duplex scanning operation on the document 22 is completed.
Since the first type duplex scanning apparatus contains a single scanning module, the document should be transferred through the scanning module for three times while one duplex scanning operation is performed by this duplex scanning apparatus. Therefore, the first type duplex scanning apparatus is referred as a three-pass duplex scanning apparatus.
Hereinafter, the structure of a conventional second type duplex scanning apparatus will be illustrated with reference to FIG. 3. FIG. 3 is a schematic side view illustrating the structure of a conventional second type duplex scanning apparatus. As shown in FIG. 3, the conventional second type duplex scanning apparatus 3 comprises a flatbed scanning portion 30 and an automatic document feeder 31. The automatic document feeder 31 comprises a sheet input tray 311, a sheet output tray 312, a sheet pick-up module 313, a sheet transfer channel 314, plural transfer rollers 315, a first scanning module 316, and a sheet ejecting roller assembly 317. The flatbed scanning portion 30 comprises a second scanning module 301 and a glass platform 302.
The process of performing a duplex scanning operation by the conventional second type duplex scanning apparatus 3 will be illustrated as follows. Firstly, plural documents 32 to be scanned are placed on the sheet input tray 311, wherein the first sides 321 of the documents 32 face upwardly. Then, the uppermost document 32 is fed into the sheet transfer channel 314 by the sheet pick-up module 313. Then, the document 32 is transferred through a scanning window 3021 of the glass platform 302 by the plural transfer rollers 315. Consequently, the images of the document 32 are scanned by the first scanning module 316 and the second scanning module 301 through the scanning window 3021. That is, the image of the first side 321 of the document 32 is scanned by the first scanning module 316, and the image of a second side 322 of the document 32 is scanned by the second scanning module 301. After the document 32 is completely transferred through the scanning window 3021, it means that the images of both sides of the documents have been scanned. Then, the document 32 is transported to the sheet output tray 312 by the plural transfer rollers 315 and the sheet ejecting roller assembly 317. Meanwhile, the duplex scanning operation on the document 32 is completed.
Since the document is only transferred through the scanning modules once while one duplex scanning operation is performed by the second type duplex scanning apparatus, the second type duplex scanning apparatus is referred as a one-pass duplex scanning apparatus.
Moreover, the three-pass duplex scanning apparatus may be calibrated by the similar process of calibrating the above conventional flatbed scanning portion. Although the second scanning module within the flatbed scanning portion of the one-pass duplex scanning apparatus can be calibrated by the similar process of calibrating the above conventional flatbed scanning portion, the first scanning module within the automatic document feeder of the one-pass duplex scanning apparatus fails to effectively calibrated because the space within the automatic document feeder is limited. Especially, since the trends in designing the duplex scanning apparatus are toward small size and small volume, the transmission mechanism for moving the first scanning module fails to be installed within the automatic document feeder. That is, since the first scanning module fails to be moved, the calibrating operation cannot be effectively done. Under this circumstance, the scanning quality is unstable and even the scanning quality is deteriorated.
Therefore, there is a need of providing a sheet-feeding type scanning apparatus with a calibrating function and providing a duplex scanning apparatus with two scanning modules which have the calibrating functions.